skirts of a wood are finer than those in the interior.

The

loss of light in stoves and greenhouses, by diminishing the effects of exhalation, renders plants more liable to be frozen than others of the same description which are growing in the open air.

"Although the decomposition of carbonic acid by the green parts of plants is perpetually carried on under the stimulus of diffused light, and its effects may even be rendered apparent by the action of lamp-light, which gives a slight tinge of green to plants when grown in a cellar, yet in these cases the process is carried on too slowly to allow of our collecting the oxygen which is set free. But when plants are placed in the direct rays of the sun, the action is so much more rapid, that the oxygen may then be collected in sufficient quantity to produce a striking result.

"A certain portion of free oxygen is necessary for the formation of the carbonic acid generated by the process of respiration; but when this carbonic acid is decomposed and the carbon fixed, the same oxygen which is set free will serve again for a fresh formation of carbonic acid so long as there remains any carbonaceous materials in the sap. This may assist us in explaining an interesting fact described in the Gardeners' Magazine, vol. x. p. 208. It is there stated that many plants, especially ferns, have been readily grown in the smoky atmosphere of London, by placing them in boxes furnished with glass coverings hermetically sealed. In this state they have lived and increased in size during several years without any immediate communication with the atmosphere.

The following succinct corroborative evidence is from the recent work of a philosophical Meteorologist, and we give it with much pleasure :

"This leads us to refer to a speculation of M. Adolphe Brongniart, upon the formation of those carboniferous beds which are so widely distributed over our globe, and without which civilization would not have rapidly advanced. To this geologist it has occurred that, during that era of our earth's history, the atmosphere was much more largely charged with carbonic acid gas than now or previously.

During that era there seems to have been an ascendancy in the vegetable over the animal kingdom; for, while immense numbers of

* Botany, in Cab. Cyc. pp. 186-194.

trees and arborescent ferns and smaller plants existed, scarcely a vestige of land animals is to be found. If we suppose that during that period there was a larger proportion of carbonic acid in the air than now, it would be most favourable to vegetable life, while the excess would be detrimental to that of animal existence.

"No sooner were those vast coal fields deposited, than we find a manifestation of animal life, and, finally, its predominance. We find much luxuriant vegetation in the presence of those waters which are richly charged with carbonic acid gas."*

These explanations of the phenomena attending the organization, the respiration, and the evaporation of perfect flowering plants, together with the manner in which they form and decompose carbonic acid, are amply sufficient to shew that sunlight and atmospheric air are indispensably requisite for effecting those important functions of the vegetable economy; and consequently, it is quite unnecessary to prove that none of the flowering plants requiring these essential elements could have existed previously to the formation of the light and of the atmosphere, and are, therefore, to be considered as not having, in any way whatever, contributed to those widely-extended and important labours performed by the agency of plants during the protracted period of non-rotation. They may, we think, after a few further explanations, be eliminated entirely from our future argument. They did not then exist.

But, in order to leave no lingering doubt unremoved, let us next enquire whether they could have fulfilled the end of their being their reproduction-had they been submerged in water. We shall first recapitulate the hundred and eighteenth Theorem: That all the phenomena attending the flowering of plants and the dihescense of the various receptacles which are instrumental in the fertilization and maturation of the SEED and FRUIT, and the dissemination of the former, fully attest the absolute necessity of these COMPLICATED OPERATIONS BEING CONDUCTED IN ATMOSPHERIC AIR. The presence of much moisture being prejudicial to the peculiar development of the pollen; and, in continuation, we shall give a few corro

* Introduction to Meteorology, by Dr. Thomson, pp. 13, 14.

borative extracts, the Theorem itself being almost sufficiently conclusive :

"It is further essential," says Prof. Henslow, "that the pollen should be protected from the influence of moisture; and, consequently, we find that aquatics, as the water lily (Nymphæalba), elongate their flower stalks until the blossoms float upon the surface of the water. In the water-soldier (Stratiotes Aloides), water-violet (Hottonia Palustus), and others, the entire plants float to the surface of the water during the period of flowering, but live submerged at other times. In the Zostera Marina the flowers are arranged within a cavity filled with air; and thus, although they are developed beneath the surface, they are protected from the immediate contact of the water.

"If ripe pollen be placed in a tub of water and examined under a miscroscope, in a few seconds it will be seen to dilate, burst, and violently expel a cloud of minute granules. These granules are still contained within the inner membrane of the pollen grain protruded through the ruptured outer membrane, but which is difficult to be observed on account of its extreme tenuity. It thus forms a sort of rude sack, termed " a pollen tube," and contains a liquid, the fovilla,' in which are dispersed a number of very minute 'pollen granules.' In consequence of the effect thus produced on pollen by water, it is liable to injury in rainy seasons, and the fertility of the seed is often impaired.

"The salt of sea water produces an injurious effect upon the seeds of plants, and completely destroys the vitality of those which are long subjected to its influence."*

"When the flower unfolds," observes the writer on Botany in the Library of Useful Knowledge, "the anther is a tolerably solid, moist body, filled with moist pollen. The grains of the latter contain a fluid more dense than the tissue that forms a covering for them, and rapidly absorbs its moisture from the anther case. As soon as this has happened to any great extent, the tissue of the anther case contracts, and at first rends into grated cells of various forms; as the dryness is increased, these latter contract still farther, and exercising a general power over the whole surface of the lining would, in the end, be rent into still finer portions, if it were not for the

Botany, in Cab. Cyc. pp. 263, 266, 303.

slight degree of cohesion which exists between the valves of the anther at the sutural line."*

These quotations, which we have considered it necessary to give as conclusively as possible, sufficiently prove that atmospheric air is not more essential to the entire phenomena connected with the development and reproduction of the Monocotyledonous and Dicotyledonous plants than that an undue degree of moisture is prejudicial to these functions: consequently, deprivation of the light and atmospheric air and submersion in water would have been altogether destructive of those important functions in flowering plants. They could not, in such a condition, have existed. But, on the other hand, as the most perfect wisdom pervades the whole design of Creation, it is but just to conclude that an adequate motive existed for the adoption of whatever principle may be evidently traceable in it. There is a principle peculiarly observable in the formation of the Vegetable Kingdom. The two great classes of plants which were called into existence after the formation of the light, the atmosphere, and the "dry land," were flowering plants, whose submersion in water, as we have just seen, would have been wholly destructive of their propagation; while those which existed before were flowerless plants possessing neither stamen, stigma, nor pollen, radicle nor plumule; therefore it is allowable to conclude that light or atmospheric air were not indispensably essential, nor was water inimical to the maturation, or to the subsequent development and germination of their reproductive bodies, whether these were sporules, cones, or dot-like bodies.

* Library of Useful Knowledge, p. 109.

SECTION III.

THE VEGETABLE ORGANISMS OF THE NON-ROTATORY PERIOD.

CHAPTER VI.

The assumed condition of the primitive vegetation compared with Botanical descriptions of Cryptogamous plants. Characters and habitats of these given in detail, and found to coincide with the supposed state of the submerged vegetation of the anti-rotatory period. Motives for supposing that there was only one general elevation of the terraine portion of the earth. The absence, in lists of fossil flora, of certain orders of Acotyledonous plants accounted for. Capability of plants growing in the waters of the primeval ocean, although this held in solution saline materials.

THE important results to which we came at the conclusion of the preceding chapter will be greatly confirmed should it be found that what, in it, was deduced from reasoning a priori, agrees with that which experimental botanists declare to prevail amongst those interesting objects of the vegetable kingdom which are now under our consideration; for, if those two branches agree we can scarcely any longer entertain a doubt. According to the foregoing consolidated lists, the plants found in the stratified masses which have been identified and classed consist of 1. Algæ. 2. Filices. 3. Characeæ. 4. Lycopodiaceæ. 5. Marsiliaceæ. 6. Equisetaceæ. 7. Naiades or Fluviales. 8. Cycadeæ. 9. Euphorbiaceae, with a few Coniferæ and Palmæ, some Cannæ, and others still uncertain as to class and genera, which consequently cannot be taken into account. But to those which have been identified we shall affix, in the order